The invention relates to a drive system for escalators and moving walkways.
It is generally known that escalators or moving walkways are indirectly or directly driven by electric motors. For an indirect drive, there is provided at least one reducing gear, and if necessary, power dividers can be additionally provided, in the region of which the components of escalators or moving walkways can be driven together. Such components included the step or pallet band, and the handrail if required and if no separate drive means is provided for the same. The step or pallet band is usually displaced by plate link chains, the direction of movement of which is changed in reversing areas via reversing elements in the form of chain wheels. An essential requirement of escalators and moving walkways is to enable the reversing of the step or pallet band without the undesired polygon effects and to obtain a synchronous running of the step or pallet band and the handrail, when they are driven together, so that one component does not run at a higher or lower speed than the other, which could cause passenger injury.
With a view toward optimization of the drive concept, plate link chains can be used for the step or pallet band, which chains also have a greater pitch depending on the step or pallet width, for example approximately 200 or approximately 400 mm. However, it is possible that these desired greater chain pitches will cause problems with respect to the polygon effect during the reversing and possibly with respect to the synchronous drive of the handrail.
Escalators and moving walkways are furthermore generally known which are intended for indoor use, for example in department stores or the like, and which are provided with drive chains, in which, with regard to the relatively low forces, the step or pallet studs including the rollers, which cooperate with the steps or pallets, are positioned in the respective joint areas of the drive chains. However, during the reversing of the reversing chains, in particular with greater chain pitch, the existing polygon effect causes problems.
German patent document DE-A 19 849 236 discloses a method and a device for guiding a chain in the area of chain wheels of a continuous conveyor system, in particular an escalator or a moving walkway, by supplying the chain to the respective chain or driving wheel in a linear direction. After engagement of a first element of a first chain link of the chain strand with the chain or driving wheel, a continuous adaptation of the effective chain radius is realized, while setting a constant velocity in the chain strand. Preferably, the chain or driving wheel shall be small, in particular in the area of the outer diameter thereof, for receiving the chain studs, wherein at least one rail-like guiding profile is placed in this area, directly beside the chain or driving wheel.
This measure permits an efficient reduction of the polygon effect, but the construction effort both in front of and in the area of the reversing wheel is high.
From German patent document DE-A 0 711 725 a similar device for guiding a band continuum of escalators or moving walkways is disclosed. In this band continuum, the chain rolls are guided by means of a supporting rail with a running path and an equalizing rail with a running path. At the entry of a chain wheel, which reverses the band continuum, the chain rolls run from the linear running path of the supporting rail onto the curve shaped running path of the equalizing rail and from there to a tangent point into engagement with the chain wheel. From the running path of the supporting rail to the tangent point, the chain rolls are guided into a direction orthogonal to the running direction, over a distance which is transverse to the running direction, towards the chain wheel, which has an advantageous effect on the quiet running of the band continuum.
This special curve shape of the connection element helps to reduce the polygon effect. In the reversing of the chains of escalators or moving walkways by means of a chain wheel, polygon and revolution effects occur, which in particular adversely affect the quiet running of the escalator or the moving walkway. The polygon effect is caused by the polygonal rest of the chain on the chain wheel. With increasing rotation angle, the effective radius of the chain wheel varies, whereby the velocity of the chain oscillates between a maximum and a minimum value. When engaging the chain wheel, the chain rolls and the teeth of the chain wheel have different velocities, which cause impacts. The revolution effect is caused by the angular momentum which is transmitted from the chain wheel onto the chain links and thus onto the steps or pallets. After the chain has run out of the chain wheel, this angular momentum is temporarily maintained due to the inertia of the system, which leads to the so called curling of the chain. The angular momentum is reduced by friction in the chain respectively by impacts between chain and guiding element, if a chain guiding element is provided.